RCBH928 wrote:So why don't USA takes military action against Russia just like they did with Saddam when he invaded Kuwait? Why was the destruction of 2 buildings and death of 3000 civilians was a good enough reason to invade 2 countries in a ten year plan but invading a whole country is not?
Nuclear weapons.
Russia may have a large military, but it has an enormous territory and lacks the infrastructure to move that military around to any particular problem area in a swift manner. If a nation like China or the United States were to invade Russia, there's little the Russian military could do to hold territory, and they would likely cede control of large swathes of land while waiting for favorable conditions and knowing that any taken territory would also likely be too large for an invader to continue to hold. Russia also has other defenses, such as particularly brutal winters and the willingness of Russian citizens under occupation to become partisan forces waging guerrilla campaigns.
But above all else, Russia has the largest nuclear stockpile in the world(about 1000 more than the US, though the US has more nuclear arms active and ready for deployment at any given time), and as of 2000, their military doctrine focuses on using nuclear arms as a deterrent, particularly against nations they perceive to be stronger than the Russian military(meaning US and NATO members). In 2009, Russian Security Council Secretary Nikolai Patrushev openly considered the use of nuclear arms in "local conflicts" such as Chechnya or the Russian invasion of Georgia, though this resulted in a public backlash, and in 2010 Russia released a new military doctrine governing nuclear arms that stated they could only be used in the event of Russia's existence being threatened. This primarily means massive and open warfare of the kind that you are suggesting.
So there you have it. In the event of a US/NATO invasion of Russia, Russia will launch its nukes as per its nuclear doctrine. Such an attack will result in an inevitable nuclear counterattack from the United States, as per its own retaliatory nuclear doctrine(US nuclear doctrine was also expanded in 2001, and while narrowed a bit in 2010, is still openly for use as a deterrent and in retaliation for a nuclear strike from any nuclear armed nation. For the record, current US nuclear doctrine[circa 2010] also reserves to right to launch nuclear counterattacks in the event of biological weapon attacks, even from non-nuclear armed nations). So we don't invade Russia. No one invades Russia for fear of nuclear attack and potential armageddon.